The proposed research is aimed at determining the molecular dynamics of the formation, breakdown and contraction of the actin, myosin and associated protein based cytoskeleton in non-muscle cells. The molecular events involved in muscle contraction will be compared with the motile events in amoeboid cells. Motile models of cytoplasmic structure and contractility will be prepared in order to determine the ionic requirements for maintaining non-motile cytoskeletons and the induction of contractions. The structure of these functional extracts will be determined by the combined use of electron microscopy and quantitative polarized light methods. Furthermore, a new concept of in vivo cytochemistry will be used in conjunction with quantitative polarized light and fluorescence microscopy to localize and to characterize the molecular dynamics of both the cytoskeletal and contractile proteins. The physiological parameters of free calcium ion concentration and pH will be related to the structural events in vivo. Furthermore, the major proteins involved in the cytoskeletal and contractile functions will be isolated and reconstituted into a functional model. Finally, the involvement of the plasmalemma in anchoring and regulating the cytoskeleton will be investigated.